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A Contribution to the Frequency Analysis and Transient Response of Power Transformer Windings

ELECTRIC POWER COMPONENTS AND SYSTEMS 2014年第11期42卷 1143-1151页

作者： Saied, Mohamed Mostafa Kuwait Univ Dept Elect Engn Kuwait Kuwait

This article proposes a new approach to study the frequency response and the transient analysis of power transformer windings. For improved accuracy, the suggested model includes, among other equivalent circuit elements, the mutual magnetic couplings between any winding turn and all others. This implies that the equivalent inductance of any considered turn will be a location-dependent parameter. Accordingly, the winding will be analyzed as a non-uniform transmission line. Through the application of a recursive circuit reduction technique, a closed-form Laplace s-domain analytical expression for the winding's input impedance can be obtained for any neutral treatment. The resulting expression can be used to determine the winding's series and parallel resonance frequencies. The s-domain expression for the input impedance, in connection with the numerical inverse Laplace transform, will be utilized for determination of the winding's time-domain transient response for any input voltage or current time waveform. Accuracy increases with the assumed number of winding sections, which can be even increased to the actual number of turns, limited only by the available computation resources. The results of case studies are in good agreement with those available in the literature using the time-domain solution of the simultaneous differential equations in the state variables.

关键词： power transformers equivalent circuit power system transients transformer winding distributed parameters simulation high-frequency model frequency response resonance

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Incipient Fault Location Method of Cable Based on Both-End Electric Quantities

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IEEE ACCESS 2020年 8卷 219503-219512页

作者： Pan, Wenxia Li, Ye Sun, Kai Zhu, Zhu Li, Xinrui Hohai Univ Coll Energy & Elect Engn Nanjing 211100 Peoples R China State Grid Jiangsu Elect Power Co Huaian Power Supply Branch Huaian 223003 Peoples R China Tongling Univ Coll Elect Engn Tongling 244000 Peoples R China

The early fault of a cable is usually a incipient fault, which is difficult to find and can easily develop into an insulation breakdown fault. Thus, it is of great significance to quickly and accurately find an incipient cable fault. This paper presents an fault location method for cable insulation based on the electric quantities of both ends. Based on the equivalent circuit model of three-phase single-core cable distribution parameters, the calculation method of the voltage along the cable is derived. The equivalent model of cable insulation in resistive and capacitive parallel is proposed and applied to the early fault modeling of cable. On the basis of the calculation formula of the voltage along the cable and the electric quantity at both ends of the cable, the analytical expression of the cable fault location is obtained by solving the fault equation directly. Extensive simulations show that the algorithm, this method can locate the incipient fault accurately, and is not affected by the fault point, fault resistance and fault inception angle.

关键词： Power cables Power cable insulation Cable shielding Mathematical model Circuit faults Licenses Aging Cable insulation fault location distributed parameters equivalent model sheath current

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Inception of transients and transient suppression methods

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INTERNATIONAL TRANSACTIONS ON ELECTRICAL ENERGY SYSTEMS 2014年第1期24卷 141-152页

作者： Brandao Faria, J. A. Univ Lisbon Inst Super Tecn Inst Telecomunicacoes P-1049001 Lisbon Portugal

This tutorial paper offers a fresh perspective on the analysis of transient phenomena. The subject, that pervades all areas of electrical engineering, is of special importance in power and energy systems where voltages and currents can have very large magnitudes and where transient events can cause power quality problems. Two main aspects are addressed in the paper: the inception of transients and transient suppression methods. The analysis of transient inception requires the consideration of short time scales where capacitive and inductive distributed effects must be accounted. The analysis of transient suppression methods, applied to an LR-circuit driven by DC or AC voltage sources, is illustrated with a two-switch technique where long time scales are appropriate. Copyright (c) 2013 John Wiley & Sons, Ltd.

关键词： distributed parameters power systems education time scaling transient analysis transient suppression

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Analytical expressions for per-unit-length parameters of finite length transmission lines with discontinuities

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IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATIBILITY 2002年第3期44卷 478-481页

作者： Ye, CF Li, EP Inst High Performance Comp Singapore 117528 Singapore

Analytical expressions for per-unit-length parameters of finite-length transmission lines are derived and verified by the method of moment in this paper. The line can be a conductor with bends and varying sizes. The expressions are explicit in form and can be used to model and analyze the effects from ends and bends on the line effectively.

关键词： distributed parameters method of moment nonuniform transmission line signal integrity

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A Multicomponent distributed Parameter Model for Spray Drying: Model Development and Validation with Experiments

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DRYING TECHNOLOGY 2013年第13-14期31卷 1513-1524页

作者： Wang, Shuosi Langrish, Tim Adhikari, Benu Univ Sydney Sch Chem & Biomol Engn Sydney NSW 2006 Australia Univ Ballarat Sch Hlth Sci Mt Helen Vic Australia

A distributed-parameter model was developed based on previous work to simulate the spray-drying process for droplets, including the diffusion and solubility of multiple components (sugars and proteins), and was extended to estimate the water activity of a multicomponent solution and to account for the surface activity of the protein. The ordinary differential equation (ODE) solver for ordinary differential equations was altered to specify the time step for the simulation. Regridding was also carried out routinely to counter the numerical problem of thinning layers. This model was then validated with drop-drying experiments that measured the rate of drying of solution droplets using having 4mg initial mass and 1-10% (w/w) initial solid concentration at 65 and 90 degrees C. The effect of air velocity past the droplets was maintained at 0.5-1m/s. Lactose and sodium caseinate were used as a model sugar and model protein and their mixtures were used as models of sugar-protein mixtures. It was found that solubility did not contribute significantly to the component segregation process and that the diffusion-convection mechanism of the solvent in solid matrix, as well as the surface activity of casein, both contributed to the accumulation of casein on the product surfaces.

关键词： distributed parameters Drop drying Model Multicomponent Protein

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Universal database for dynamic simulation

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SIMULATION 1995年第5期65卷 293-303页

作者： Chen, FFK Moncrief, BR WESTINGHOUSE SAVANNAH RIVER CO AIKENSC 29802

In today's process plant design environment, steady state flowsheet simulations are fairly routine practices. With today's microprocessor power, with availability of capable and cost effective software, desktop dynamic models of entire plants are a practical reality. With such information age power tools, possibilities are infinite. Not the least is that the many what-if scenarios surely will enlarge the design parameter space, ensured by a systematic procedure in quality design, all at reasonable cost. With the multitude of software platforms, reusable (universal) models are cost effective. More significantly, these can be a boon to the credibility issue. The ability to take a complex model, developed elsewhere on an unfamiliar platform, plug into one's favorite simulation software and be operative without the pain/effort in re-engineering the entire model database can surely promote increase in usage of dynamic simulation among plant designers. A universal database is proposed to facilitate portability of models among language platforms. In this paper, portability of large complex models is proven by two examples (from plant design) on two platforms (DAP and ACSL). This paper illustrates the database requirements to allow models to commute between vastly different platforms, using specific examples to arrive at a more universal conclusion.

关键词： universal database model portability ACSL DAP plant models distributed parameters lumped models

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MULTICONDUCTOR TRANSMISSION-LINE MODEL FOR THE LINE-END COIL OF LARGE AC MACHINES

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IEE PROCEEDINGS-B ELECTRIC POWER APPLICATIONS 1985年第3期132卷 149-156页

作者： MCLAREN, PG ORAEE, H Engineering Department University of Cambridge Cambridge UK

This paper describes how the PE2D finite-elements field package is used to calculate the distributedLandCparameters of a multiconductor transmission-line model for the line-end coil of a large AC motor. Under steady-state AC conditions, the package produces field distributions from which self and mutual inductances and capacitances can be calculated. distributed shunt and series losses are included in the model, and there is no need for any assumptions about surge velocities in evaluating the coil response. Separate parameters are calculated for the slot and overhang regions and the various sections of uniform multiconductor transmission lines are joined in series to represent the complete coil. The coil response is then computed using a Fourier transform technique. The input waveform is broken down into its spectral components and the steady-state transmission-line equations are solved at each component frequency. The response at each frequency is then used in the inverse Fourier transform to arrive at the solution in the time domain. Responses calculated from the model are compared to test responses on a laboratory model of the line-end coil and are found to be in good agreement. Several parameter variations are then investigated on the theoretical model.

关键词： a.c. machines AC motors steady-state AC conditions distributed parameters line-end coil distributed series losses Power engineering computing Interpolation and function approximation (numerical analysis) multiconductor transmission-line model electric machine insulation electric machine analysis computing input waveform overhang regions distributed shunt losses coil response large AC machines Fourier transform technique spectral components Fourier transforms Integral transforms PE2D finite-elements field package Numerical analysis finite element analysis machine insulation

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Offense control taking into account heterogeneity of age

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JOURNAL OF OPTIMIZATION THEORY AND APPLICATIONS 2003年第3期116卷 591-620页

作者： Hartl, RF Kort, PM Feichtinger, G Univ Vienna Dept Business Studies Vienna Austria Tilburg Univ Dept Econometr & Operat Res & Ctr NL-5000 LE Tilburg Netherlands Vienna Univ Technol Dept Operat Res & Syst Theory Vienna Austria

This paper studies the optimal tradeoff between the benefits and costs of preventing offenses and treating offenders. Based on a flexible age-structured epidemiological framework, a two-state compartment model is analyzed to reduce the prevalence of offending such as illicit drug consumption or violence. It turns out that, even in this highly simplified model, multiple stationary states exist. In particular, three different kinds of equilibria are identified, i.e., law and order, conservative, and liberal. The optimal mix of the control instruments is calculated providing interesting insight into the structure of the paths minimizing the discounted stream of social costs and expenditures for prevention and treatment. It can happen that a Skiba point exists. This implies that, for an initially small number of offenders, saddle-point convergence to a law-and-order equilibrium (boundary solution with no offenders) or to a conservative equilibrium (with few offenders) occurs, while if the number of offenders is large, the effects of prevention and treatment are too low or too expensive so that a liberal equilibrium (with many offenders) occurs.

关键词： optimal control thresholds Skiba points distributed parameters partial differential equations multiple equilibria economics of crime

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Approach for modelling of broadband low-voltage PLC channels using graph theory

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IET COMMUNICATIONS 2018年第13期12卷 1524-1530页

作者： Zhao, Xiongwen Zhang, Hui Lu, Wenbing Li, Liang North China Elect Power Univ Sch Elect & Elect Engn Beijing 102206 Peoples R China

Broadband power line is an important way of communication in low-voltage distribution networks because a power line is everywhere nowadays. However, due to the heterogeneity of a practical power-line network and various loads connected to its termination points, modelling and simulation of power-line communication (PLC) channels are difficult and complicated issues. In this work, the authors propose a novel PLC channel modelling approach using graph theory for the first time when knowing the power-line network topologies and cable distributed parameters. The approach utilises simple and effective recursive operations in solving the k-shortest paths to estimate the channel transfer function for a specific power-line network, it overcomes the complicated analytical derivation in computing the channel transfer function by the traditional two-port network in the bottom-up model and avoids to measure the actual channel in a top-down model. Their proposed approach is validated by transmission-line (TL) theory as well as measurement results, and it is also compared with TL theory. The results show that their proposed PLC channel modelling approach herein is simple to be implemented, it is expected to have extensive applications in broadband PLC systems for performance evaluations.

关键词： carrier transmission on power lines transmission line theory graph theory distribution networks telecommunication network topology broadband low-voltage PLC channel modelling graph theory broadband power line low-voltage distribution networks power-line communication channel simulation power-line communication channel modelling power-line network topologies distributed parameters k-shortest paths channel transfer function estimation traditional two-port network bottom-up model top-down model transmission-line theory TL theory broadband PLC systems

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Accurate one-end fault location for overhead transmission lines in interconnected power systems

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INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS 2010年第5期32卷 383-389页

作者： Eisa, Amir A. A. Ramar, K. Multimedia Univ Fac Engn Cyberjaya 63100 Malaysia

This paper presents a new one-end fault location method for overhead transmission lines embedded in a general n-bus interconnected power system. High accuracy in fault location is achieved by using both an accurate distributed parameters model for the faulted transmission line, and a two-bus Thevenin equivalent network model for the power system that accurately accounts for its interconnectivity. The method has been tested using transient fault data obtained from PSCAD/EMTDC simulations of an 11-bus interconnected power system. The results obtained indicate that the method is capable of estimating the fault distance with high accuracy for various fault conditions. They also indicate that method is sensitive to errors in the value of the local bus impedance, but is insensitive to errors in the value of the remote bus impedance. (C) 2009 Elsevier Ltd. All rights reserved.

关键词： Fault location Transmission lines distributed parameters One-end measurements

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